Phew! Long time no post! I apologize for the delay–I have begun a series of days where I take children from kindergarten through 8th grade out to experience nature. I take one grade at a time and show them things on their school grounds and/or take them to a local nature area, like part of a creek or a tree nursery. It has been a busy few days, especially because the rain called for some impromptu in-door lessons to replace what we would have done outside. They have been a lot of fun, and I hope to write more about them sometime soon. For now, though, I want to write about something I saw on my first day out with a class early this week.
A few days ago I took a kindergarten class out to explore the school grounds and see what adventures we could find. We did an “environmental scavenger hunt,” where I told them different things to do, like find a seed, or discover if all of the yellow flowers in the yard were the same, and then they searched for answers. At one point I sent them to look for insects, and one of the students called me over to point out a leaf that had been chewed on and eaten. How clever! I was very excited that this child understood that even if he didn’t see the insect itself, he knew an insect had been there because of the holes in the leaf where it had eaten! That is exactly the type of thinking we need to foster, and could all benefit from!
We talked in the Doorways to Nature post about picking a certain thing to look for on walks (or any time we leave the house) to give a little more variety to our day and try to expand our horizons. On a recent walk I decided to look for insect ‘damage’ to see how much of it I could find. Insect damage is the term used for any kind of insect signs usually found on a leaf. It can be one of the different types of insect feeding, a place an insect has laid eggs on the leaf, or a place where an insect has changed the leaf to make a shelter.
Here is a leaf I found that had hole feeding. True to its name, hole feeding is just when an insect has eaten a hole through a leaf! It can be fairly circular, like this one, or have more irregular edges. See the lighter edges around the hole? This is where the plant has begun to heal around the place the insect ate. This is very important, so remember it for a little farther down in the post!
Here is some more hole feeding, along with margin feeding, which is when an insect feeds along the edge of a leaf. There is also some kind of growth on the plant–I am not sure if it is related to the insects or not, and will have to do some more research on that.
Until about 5 years ago I never really thought about insect damage. Then I helped a graduate student one summer with her research looking at insect damage preserved on fossilized leaves. We spent the summer digging up leaf fossils in the Bighorn Basin of Wyoming, and then searching the fossil for signs of insect feeding. The fact that not only a delicate leaf but also the signs of something living on the leaf could be preserved for so long–the leaves we were looking at had lived and died ~55 million years ago–really amazed me, and forever changed the way I look at leaves and insect feeding.
Remember the ring around the hole feeding where the plant is healing that I mentioned earlier? That ring is very well-preserved in the fossils, and is a great sign of insect damage. Here is a picture of one of the leaves we found that summer that was later used on the cover of Science:
[Photo taken by Scott Wing, Smithsonian Institution]
The dark ring around the holes in this fossil leaf are how we know the hole is from insects feeding when the plant was still alive, and not holes made afterwards from decay or damage to the fossil.
One of my favorite types of insect feeding, and one that–believe it or not–is also preserved in fossil leaves is called skeletonization.
It was difficult to get a close up of this without picking the leaf off the tree, but notice the lighter areas around the edges of the plant? This is where all of the layers of the leaf except the veins were chewed away.
When I was in Wyoming for that summer in 2005 I found a living tree that had almost all of the different kinds of insect damage on it that we were finding in the fossils. I pulled leaves off that represented each one and used packing tape to preserve them in my field journal. They have held up remarkably well so far, and the example of skeletonization is especially clear:
There are other types of insect damage as well. The list could go on and on, but the other kind that I enjoy finding the most is mines, where an egg is laid inside the leaf and an insect chews its way out, leaving its droppings behind. I didn’t find any on my recent walk, but here is a photo example from this wikipedia page:
Searching for insect damage is a great way to learn more about the habitat around you. Are there a lot of insects feeding? Or just a few? Is there only one kind, or are there many? Take a look at the trees and bushes next to where you park your car, or by the building where you work–it could be anywhere, and you don’t have to go on long walks to find it! Let’s see what we can learn about the great drama of Life going on around us by searching for the marks that are left behind.
As always, please feel free to send me photos of anything you find! I would love to learn more about what is around you, and what adventures you have had!